Spider mites can do a lot of damage to many kinds of plants during the summer, including tomatoes, lima beans, roses and spruce trees. I've gotten reports of their presence in several gardens.

Tiny creatures, barely visible to the naked eye, they suck juice from the foiliage. They multiply rapidly, the females laying 100 or more tiny, round, whitish eggs that hatch within five to seven days. A heavy infestation can cause serious damage to the plants they feed on.

The mites build an extensive system of webbing, much more dense than the average spider web, for their travels. The webbing also keeps the mites off treated surfaces during feeding and intercepts spray particles.

The mites' feeding turns leaves of lima and snap beans rusty red and causes many leaves to drop. Use of Sevin to get rid of Mexican bean bettles and other insects favors the mites because it kills their predators.

A lot of gardeners have been able to reduce the mites' numbers by using a high-pressure nozzle on the water hose. Spray the foliage once a week with the water under pressure. Apparently the pressure of water knocks the mites off the branches and onto the ground. On large evergreens spray as high as they can be reached from the ground.

But much better control can be obtained by spraying with miticides. To control mites on food plants use Kelthane or Spectracide. Directions on the label should be followed closely. To control mites on spruce and other conifers use Kelthane or Dimethoate. But before using them, check for the mites' presence. Hold a piece of white paper beneath a branch and tap the branch sharply. if little brown specks move on the paper the use of a miticide is justified. But check several branches, because some will have more mites than others.

It's a good idea at this time of the year to check your English boxwood to see whether the plants have become so compact that little light and air reach the center of the crown, according to Albert Beecher, Virginia Tech horticulturist and president of the American Boxwood Society. Too little light and air can kill the interior shoots and weaken the plant.

Pruning some of the inner branches will help to open the plant up to light and encourage a green center where there will be green leaves all the way up the stems.

Check also to see whether you have an accumulation of dead leaves inside the plants.At least once a year clean outleaves or twigs that have accumulated in the centre of the boxwood - otherwise, fungus grows more easily on leaves and twigs, interior shoots get stunted and roots may grow up around the branches. Not cleaning dead leaves out can be a major factor in contributing to boxwood decline, Beecher says.

Q - We started a new lawn from seed this spring. We watered it 10 or 15 minutes every day and it was doing fine. Then we went away for a week and when we returned the grass was almost dead. Do you have any idea of what could have been wrong?

A - When the lawn is watered, it should be moistened to a depth of six to eight inches at least. This requires one or two inches of water, which a sprinkler can supply in four to six hours.

Sprinkling 10 or 15 minutes every day brings the grass roots to the surface for moisture because the water does not penetrate deep enough to reach them. Then when you stop sprinkling, even for a few days, the soil dries out quickly and the roots die.

Q - Ladybugs are supposed to protect my beans from insects but instead they are eating my plants. How come?

A - Not all ladybugs are benefecial to plants. One black sheep in the family is the Mexican bean beetle, which eats plants instead of other insects. The adult lady beetle (ladybug) has 12 small black spots on reddish wing covers. The Mexican bean beetle is somewhat larger and is coppery yellow with 16 black spots, eight on each wing cover.

The Mexican bean beetle produces two, three or four generations a year, depending on the latitude, and is especially destructive to beans. Spraying or dust treating with Sevin is recommended if there is a large number of them; otherwise, pick them off. If you spray, follow the directions on the label closely.

Q - I bought a large croton a couple of months ago and it has lost almost all of its leaves, one by one. I keep it on the windowsill where it gets midday and afternoon sun. It's so handsome, can you tell me how to keep it alive?

A - Croton (codiaeum) is rather out of place indoors in the average home because it needs morning sun and high humidity, at least 40 percent during the summer and 30 to 40 percent in winter.

Midday and early-afternoon sun during the summer may burn the plant, particularly if it has been out of the sun during the morning.

The soil should never be allowed to dry out. When the soil feels dryish, water until water comes out of drainage holes, wait about 15 minutes for excess water to drain and empty the saucer. If the pot stands in water for long the roots will be damaged.

Q - I see people putting grass clippings around their shrubs and flower beds.Is this good for them?

A - Grass clippings make an excellent mulch, but they should be mixed with oak leaves before being used. When they get wet they mat and in that condition they are a nuisance.

Q - I have two birch trees in my front yard. Last year they were simply lovely, although they lost their leaves early in the summer. This year they are a mess. Greenery has appeared in the joints or forks of the trees only. What's up, do you suppose?

A - Probabilities are your birch trees are the victims of bronze birch borers. They mine just under the bark, which is loosened . The first sign of injury is the drying back of trees at the top, by which time it is rather late for control measures. The entire tree usually dies in a short time, Outside their natural range, birch trees are very susceptible, particularly those that are not vigorous.

Q - I want to plant some primroses but my daughter insists they are poisonous to animals and we have two tiny poodles and two cats. Would primroses hurt them?

A - Primroses that grow outdoors the year around are widely planted and are not considered hazardous except possibly to those allergic to them. They are not rated as hazardous to dogs, cats or birds